The present invention relates to a display device which projects an image onto a screen with use of light valve elements such as liquid crystal panels. In particular, the present invention is concerned with a projection type image display device such as an LCD projector or a rear projection type display device.
A projection type image display device such as an LCD projector or a rear projection type display device has heretofore been known. In such a projection type image display device, light emitted from a light source such as an electric bulb is subjected to light intensity modulation for conversion of the light into light and shade for each image in accordance with an image signal by means of light valve means such as liquid crystal panels to form an optical image and the optical image is projected as image on a larger scale onto a screen or the like.
Many of the projection type image display devices available recently operate as follows. Light emitted from a light source is split into light rays of plural colors (e.g., three colors) by a light splitting means, and the light rays are then modulated by light valve means taking charge of the respective colors (in the following description the light valve means are assumed to be liquid crystal panels for convenience' sake). The modulated light rays are passed through a synthesizing prism so that light having plural color components is obtained, the light obtained thus is then projected through a projection lens to the exterior of the device and is displayed as image.
In this case, it is necessary for the synthesizing prism and the liquid crystal panels to be in a positional relation such that the plural components, e.g., three-color components, are all fixed. If even one of the three liquid crystal panels is displaced, a color shift or a focal shift will occur in the synthesized display image, with the result that the quality of the image is impaired.
In a conventional manufacturing process for a projection type image display device using liquid crystal panels as light valve means, when the liquid crystal panels are to be mounted around a synthesizing prism, a so-called convergence adjustment is performed. This convergence adjustment involves adjusting the posture and position of the liquid crystal panels and making sure that three-color components' images are coincident in the projected image. After the convergence adjustment, the liquid crystal panel is fixed at the respective positions relative to the synthesizing prism by bonding for example.
A conventional method wherein liquid crystal panels are fixed after adjusting their postures and positions relative to a synthesizing prism is disclosed, for example, in Japanese Patent laid-open No. 2002-372750. This publication describes a method wherein liquid crystal panels are mounted through a mounting member around a cross dichroic prism (hereinafter referred to simply as “prism” unless there arise any doubt) which serves as a synthesizing prism for synthesizing three-color components. Japanese Patent laid-open No. 2002-268032 discloses a construction wherein liquid crystal panels are screwed to sheet metal members and the screw portions are fused to molded members mounted in upper and lower positions of a prism. Japanese Patent Laid-open No. Hei 11-84196 discloses a construction wherein liquid crystal panels are secured to sheet metal members as support members and are thereafter bonded to a prism and a base which supports the prism. Japanese Patent Laid-open No. 2000-105434 discloses a construction wherein metallic frames attached to liquid crystal panels and a support frame attached to a prism are fused using a heat-fusing material and are mounted thereby.